5-Chloro-3-ethyl-N-(4-(piperidin-1-yl)phenethyl)-1H–indole-2-carboxamide (ORG27569, 1) is a prototypical allosteric modulator for the cannabinoid CB1 receptor. Based on this indole-2-carboxamide scaffold, we designed and synthesized novel CB1 allosteric modulators that possess photoactivatable functionalities, which include benzophenone, phenyl azide, aliphatic azide and phenyltrifluoromethyldiazrine. To assess their allosteric effects, the dissociation constant (KB) and allosteric binding cooperativity factor (α) were determined and compared to their parent compounds. Within this series, benzophenone-containing compounds 26 and 27, phenylazide-containing compound 28, and the aliphatic azide containing compound 36b showed allosteric binding parameters (KB and α) comparable to their parent compound 1, 7, 8, and 9, respectively. We further assessed these modulators for their impact on G-protein coupling activity. Interestingly, these compounds exhibited negative allosteric modulator properties in a manner similar to their parent compounds, which antagonize agonist-induced G-protein coupling. These novel CB1 allosteric modulators, possessing photoactivatable functionalities, provide valuable tools for future photo-affinity labeling and mapping the CB1 allosteric binding site(s).

Cannabinoid receptor 1 (CB 1) is a G-protein-coupled receptor that is abundant in the central nervous system. It binds several compounds in its orthosteric site, including the endocannabinoids, arachidonoyl ethanolamide (anandamide) and 2-arachidonoyl glycerol, and the plant-derived D 9-tetrahydrocannabinol, one of the main psychoactive components of marijuana. It primarily couples to G i/o proteins to inhibit adenylate cyclase activity and typically induces downstream signaling that is G idependent. Since this receptor is implicated in several maladies, such as obesity, pain, and neurodegenerative disorders, there is interest in developing therapeutics that selectively target this receptor. Allosteric modulators of CB 1 offer one new approach that has tremendous therapeutic potential. Here, we reveal receptor-and cellular-level properties consistent with receptor activation by a series of pyrimidinyl biphenylureas (LDK1285, LDK1288, LDK1305, and PSNCBAM1), including promoting binding of the agonist CP55940 with positive cooperativity and inhibiting binding of the inverse agonist SR141716A with negative cooperativity, demonstrated via radioligand binding studies. Consistent with these findings, the allosteric modulators induced cellular internalization of the receptor and recruitment of b-arrestin 2 in human embryonic kidney cell line 293 cells monitored with confocal and total internal reflective fluorescence microscopy, respectively. These allosteric modulators, however, caused G-protein-independent but b-arrestin 1-dependent phosphorylation of the downstream kinases extracellular signal-regulated kinase 1/2, mitogen-activated protein kinase, and Src, shown by immunoblotting studies. These results are consistent with the involvement of b-arrestin and suggest that these allosteric modulators induce biased signaling.

Abstract:Bedaquiline is the first FDA-approved new chemical entity to fight multidrug-resistant tuberculosis in the last forty years. Our group replaced the quinoline ring with a naphthalene ring, leading to a new type of triarylbutanol skeleton. An asymmetric synthetic route was established for our bedaquiline analogues, and the goal of assigning their absolute configurations was achieved by comparison of experimental and calculated electronic circular dichroism spectra, and was confirmed by the combined use of circular dichroism and NMR spectroscopy.

Tyrosine kinases regulate cell proliferation, survival, invasion and angiogenesis during tumor initiation and progression. The Abelson (ABL) family of protein kinases comprises ABL1 and ABL2, which link diverse extracellular stimuli to signaling pathways that control cell growth, survival, invasion, adhesion and migration. Inhibition of ABLs has been implied in many type of hematopoietic malignancies and solid tumors. The compound PD173955 is a potent ABL kinase inhibitor. It was developed from the scaffold pyrido[2,3-d]pyrimidin-7-one by Parke-Davis (Pfizer). To discover novel ABL inhibitors, we investigated the scaffold pyrano[2,3-d]pyrimidin-7-one, which is structurally analogous to pyrido[2,3-d]pyrimidin-7-one. This novel scaffold has not been extensively studied in synthetic chemistry and pharmacology. The compound LDK1504 generated from this scaffold is a close analog of PD173955. It was synthesized as a prototypical compound from the pyrano[2,3-d]pyrimidin-7-one scaffold. In the enzymatic assays, LDK1504 was demonstrated with an inhibitory activity comparable to PD173955 for ABL1 kinase. It can inhibit the ABL1 kinase with an IC50 of 18.7 nM. Further optimization leads to the identification of LDK1512 (Kd = 0.38 nM; IC50 = 1.27 nM) against ABL1. The preparation of this class of compounds was achieved through a facile synthesis of 6-bromo-2-(methylthio)-7H-pyrano[2,3-d]pyrimidin-7-one followed by Suzuki coupling reaction and derivatization of the C-2 position of the pyrimidine ring. In this presentation, our synthesis, preliminary SAR of this class of compounds, and kinase selectivity profiling will be discussed. Citation Format: Zhixing Wu, Boqiao Fu, Changjiang Qiao, Ashila Nagaraju, Dai Lu. Discovery of potent Abelson kinase inhibitors from the scaffold of pyrano[2,3-d]pyrimidin-7-one [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1661.